Dials



Oct 15 1955 H. v. ALExANDERssoN 2,767,251

DIALs Filed March 8, 1955 IN VEN ifo/ HH/Qmp 14% Dimm ,4MM/wmf By bmMyW/14 nited States Patent O DIALS Harald Valdemar Alexandersson,Lidingo, Sweden, as-

signor to Telefonaktiebolaget L M Ericsson, Stockhoim, Sweden, acorporation of Sweden Application March 8, 1955, Serial No. 492,996

Claims priority, application Sweden March 26, 19554 6 Claims. (Cl.179-90) The present invention relates to a dial for automatic telephonesystems. The gear arrangement betweeen the nger wheel and the speedregulator used in a dial is usually a wormor cog-gear. It is diicult tohave such gears work silently and in a reliable manner during a longtime. Besides, they comprise relatively many details. An object of thepresent invention is to achieve asimple construction, in which saiddisadvantages are substantially avoided. In carrying out the objects ofthis invention, a gear device consisting of a friction gear has acylindrical friction path fixed to the body of the dial, inside ofwhich, a plurality of balls or rolls, respectively, are arranged so asto engage with the friction path and actuate the speed regulator whenthe finger wheel is returning to normal position after winding. Aspecial advantage of such a constructionY is that the high bearingpressures common to friction gears are avoided.

The invention will be described more closely with reference to theaccompanying drawing, wherein Fig. l is a plan view, in section, takenalong line B-B of Figure 2, showing the gear arrangement; Fig. 2 is aside view in section, taken along line A-A of Figure l, showing a dialprovided with the gear arrangement according to Fig. 1.

Referring now to the drawing, the rigid body 1 of the dial has acylindrical inner surface 2. Inside the body and mounted in it there isa driving mechanism 3 rigidly connected with the movable finger wheel13, three cylindrical rolls 4 being mounted on studs 5 in said drivingmechanism. Outside said rolls there is a row of three balls 6, which arekept in position by a ball holder or race 7 fixed to the drivingmechanism. In the center of the driving means there is a regulator orgovernor shaft 3, to the lower part of which a regulator 9 is xed. Theregulator shaft 8, which is rotatably mounted between the three rolls 4,is arranged so that it cannot be moved axially. When the regulatorrotates its weights l move round studs 11, thereby pressing against abrake-path on the inner surface of the prolongation downwards of thedriving mechanism. The exterior surface of said prolongation is shapedas a cam disc for actuating spring sets, which are not shown. Thedriving mechanism 3 is fixed to the finger wheel 13 by means of a screw14.

The shown gear arrangement functions in the follow ing manner. If thenger wheel is wound up in the direction shown by the arrow on top ofFigure 1, the driving mechanism 3 with the rolls 4 and the balls 6 isalso driven in the same direction. The balls then irnmediately come outof mesh with the cylinder surface 2 on the body 1. The gear arrangement3, 4, 8 is thereby disengaged and the regulator 9 stands still. If thefinger wheel is released after winding up, it is in a known manneractuated by a spring device, which is not shown, so that the wheelrotates in the direction opposite to that indicated by the arrow. Duringthat return of the finger wheel the balls mesh between the cylindersurface 2 and the rolls 4, which they press against the regulator shaft8 located in the centre. If the dimensioning is such that the mesh angleof the balls 6 between the rolls 4 and the cylinder surface 2 is smallerthan the friction angle for the used material, the balls cannot slidebut roll around and pull the rolls with them, which rolls in their turnwind the regulator shaft 8. Since there is no sliding, the peripheralspeed of all the movable parts is equal, and the gear ratio is equal tothe ratio between the diameters of the cylinder surface 2 and theregulator shaft 8. Actually, the arrangement is such that the ballsfunction in rolling wedges.

The bearing pressure is usually high in friction gears, but as appearsfrom the drawing the normal pressures on all the parts compensate eachother in the proposed construction, so that they appear only as innertensions in the partaking parts. The bearing friction can therefore bekept at a low value.

In the proposed construction the cylindric surface is rigid and therolls and the balls movable as well as the finger wheel. An extremelysimple construction is thereby obtained. The cylindric surface 2 canthen be made a part of the body, which latter is suitably manufacturedof iron sheet, in which a cylindrical excavation has been stamped. Thebody is case-hardened and ground along the cylindrical surface 2.

The main part 3 of the driving mechanism is suitably manufactured ofplastic material, for example nylon, and it can be made so as tocomprise in one piece both a nave for mounting in the body 1 and a brakepath 10 for the regulator as well as an impulse disc 15 and bear ingstuds 5 for the rolls 4.

Another great advantage of the proposed construction is that the quicklymoving regulator shaft 8 needs only be mounted between the inner row ofrolls 4. It is thus squeezed between said rolls in a self centeringposition.

The invention described above is naturally not limited to the embodimentshown on the drawing, which is only an example of a suitableconstruction. The gear arrangement may thus be manufactured in someother manner. Among others, the balls 6 may be replaced by rolls. lt islikewise possible to replace the rolls 4 by balls.

I claim:

l. A dial assembly for automatic telephone systems comprising, incombination, a iixed housinghaving an inwardly disposed cylindricalfriction surface, a rotatable finger wheel disposed outwardly of oneside of said housing, a speed regulator disposed outwardly of anotherside of said housing, a rotatable shaft carried by said speed regulatorand extending into said housing, and friction drive means carried bysaid linger wheel and disposed within said housing between said frictionsurface and said rotatable shaft, said friction drive means comprising arst set of rotatable means in driving engagement with said shaft andspaced from said friction surface, and a second set of rotatable meansdisposed between said first set of rotatable means and said frictionsurface and engageable with said friction surface and said first set ofrotatable means in response to rotation of said finger wheel in onedirection and disengaged therefrom in response to rotation of saidlinger wheel in an opposite direction.

2. A dial assembly as set forth in claim l, wherein said rst set ofrotatable means comprises at least one circular element, and said secondset of rotatable means comprises at least one circular element having adiameter greater than the spacing of said first set of rotatable meansfrom said friction surface and being displaceable from a firstdisengaged position relative to said friction surface and said first setof rotatable means for one direction of rotation of said finger wheel toa second wedge-like engaged position between said friction surface andsaid first set of rotatable means.

3. A dial assembly as set forth in claim 2, wherein said shaft'isdisposed along the central axis of said cylindrical friction surface,said first set of rotatable means comprising three symmetricallyarranged friction wheels Vin constant engagement with said shaft, andsaid second ported by said finger wheel, and said Vballs are rotatablysupported by a circular race carried by said finger wheel. Y5. Adial-assembly as set forth in claim 4, wherein 4 Y v said finger wheelsupports aV brake assembly adjacent to said speed regulator. f

6. A dial assembly as set forthy in claim 5, wherein Y said brakeassembly comprises an inwardly disposed p brake path surrounding saidspeed regulator, and an exterior peripheral surface having an impulsedisc for actuating engagement with dial contact springs.

References Cited in the file of this patent UNITED STATES PATENTS1,866,669 Rhodes Julyrl2, 1932 WMA

